The present embodiments relate to a local coil for a magnetic resonance tomography (MRT) system.
Magnetic resonance tomography devices for examination of objects or patients by magnetic resonance tomography (MRT, MRI) are described, for example, in DE10314215B4.
In magnetic resonance tomography, RF coils (e.g., local coils) are used for receiving magnetic alternating fields. In order to obtain a good signal-to-noise ratio (SNR), the geometry and receive profile of the RF coils are adapted for the different areas of the body, and the coils are positioned as close as possible to the body of the patient. For fast, parallel imaging (SENSE, GRAPPA), high-channel array coils including a number of individual coils (e.g., antennas) are used. With the increase in the number of individual coils, the size of the individual coils becomes ever smaller for a pre-specified geometry. With a reduction in the size of the coils, the connection to the patient becomes less, so that the unloaded values of the coils become more important. The connection is defined via the ratio of the unloaded values to the load values. The higher the ratio is, the higher is the SNR of the coil. To improve the SNR, the unloaded value of the coil may have a value that is as high as possible, and/or the mutual influencing of the coils may be minimized. An increase in the height (h) of the copper layer of a coil does not guarantee any further improvement as from a height of approximately five times the thickness of the skin. Likewise, widening the copper layer from a width of w=pi*D does not guarantee any further appreciable value of the unloaded values. Electrical losses, which depend on the distances of the coils from one another, arise at the crossing points of adjacent coils.
Coils with very high quality are constructed from silvered, round copper wires with a diameter of approximately 1 mm. The coils have been inductively decoupled by geometrical overlapping. At the crossing points of the individual coils, the distance has been increased with a wire bridge. For coils with a normal requirement with respect to electrical quality, the antenna elements have been implemented for circuit boards (e.g., plastic carriers) copper-clad on one side. The crossing points may thus be embodied by changing the board sides. The distance may be increased by interspersion of plastic parts.